The present invention relates to the use of a photoresist mask in semiconductor device production. More particularly, the present invention relates to etching through a photoresist mask during the production of a semiconductor device.
During semiconductor wafer processing, features of the semiconductor device are defined in the wafer using well-known patterning and etching processes. In these processes, a photoresist (PR) material may be deposited on the wafer and then is exposed to light filtered by a reticle. The reticle is generally a glass plate that is patterned with exemplary feature geometries that block light from propagating through the reticle.
After passing through the reticle, the light contacts the surface of the photoresist material. The light changes the chemical composition of the photoresist material such that a developer can remove a portion of the photoresist material. In the case of positive photoresist materials, the exposed regions are removed, and in the case of negative photoresist materials, the unexposed regions are removed. Thereafter, the wafer is etched to remove the underlying material from the areas that are no longer protected by the photoresist material, and thereby produce the desired features in the wafer.
To provide increased density, feature size is reduced. This may be achieved by reducing the critical dimension (CD) of the features, which requires improved photoresist resolution. One way of improving photoresist resolution is by providing thinner photoresist masks.
New photoresist materials (193 and 157 nm PR) are being pursued to produce small CD sizes in the photoresist, but these resists are less resistant to damage from the plasma than previous masks of DIV and 248 nm photoresist. Also, with the current single layer approach, increasingly thinner resist must be used to match the resolution of the features. This may not provide enough resist for the oxide etch and may cause other complications, such as striation. In order to keep up with shrinking feature dimensions, the industry has been investigating new technologies such as multi-layer approaches involving several processing steps. The switch to new technologies will undoubtedly be expensive and time-consuming.